The use of procedural techniques for three-dimensional texturing (solid texturing), modeling, and shading in computer graphics and animation has grown rapidly over the past decade. It is now possible for three-dimensional objects and shapes created on a personal computer or workstation to be filled in with textures simulating natural materials and natural phenomena. For example, it is now common to display realistic images having textures resembling marble, wood, or stone. Likewise, computer researchers and scientists have successfully simulated natural phenomena such as fog, waves, fire, and clouds for display on a computer screen.
Texturing methods vary the point-to-point surface properties of an object to give the appearance of detail that is not actually present in the geometry. A “texture”—sometimes referred to as a “pattern” or “wallpaper”—is simply an image that used as surface covering for objects or shapes created by a graphics program running on a computer. Textures come in many varieties. Examples include bump mapping, which simulate the appearance of surface bumps without actually modifying the geometry of the object; light maps which give the appearance of smooth diffuse lighting; displacement mapping, in which textures are used actually to move the surface; and solid textures that give consistent textures of all surfaces of an object regardless of distortions of the surface parameter space.
A texture may be explicitly specified by storing all the complex details of the scene or sequence in a bit-map that contains the value of each pixel in the image. This approach obviously requires a large amount of storage space within the computer; but is it well suited for certain representations, such as a reproduction of a famous painting. Alternatively, all of the details of a given texture may be abstracted into a mathematical function or algorithm (i.e., a procedure) that is used to define pixel values. A procedural technique is defined as a code segment or algorithm that specifies some characteristic of computer generated model or effect. A procedural texture, therefore, is an image initially described—not by the pixel values—but by the operation or formula, which may include a pseudo random element, used to create the pixel values.
Procedural textures offer certain advantages over bit-mapped textures. For instance, the storage requirements of a procedural texture are generally independent of the number of pixels. That is, a procedural texture can be stored in a storage space that is several orders of magnitude less than the space required to store a corresponding bit-mapped representation. Procedural textures also provide the power of parametric control (sometimes referred to as database amplification) allowing the user to create a variety of textures that can be evaluated to any desired resolution. Procedural techniques further offer the designer the flexibility of creating completely abstract or purely artistic effects that lack resemblance to natural objects. Techniques for building procedural textures are described in “Texturing and Modeling”, Second Edition, (Chapter 2) Ebert et al., Academic Press, London (1998). Various methods of using procedural textures in graphics rendering systems are disclosed in U.S. Pat. Nos. 5,956,043, 5,949,428, 5,852,443, 5,808,617, and 5,481,669.
Current methods and systems primarily use fixed-sized, pixel-based images for textures. Few rendering applications utilize procedural textures. For instance, rendering applications and plug-ins that are designed for Internet viewing of models usually transmit compressed images. This places to significant demands on the bandwidth of the data communications medium. A typical JPEG compressed image with dimensions of 512×512 pixels, for example, requires about 75 K bytes. A procedural texture of the same image might only require 3 K bytes. Therefore, what is needed is a method and apparatus capable of taking advantage of the benefits offered by procedural textures, with backward compatibility in existing three-dimensional (3D) authoring and rendering applications that rely on traditional pixel-based images for textures.